Commonly assigned U.S. Pat. No. 5,502,445, issued Mar. 26, 1996 and 5,491,482, issued Feb. 13, 1996 disclose a system and method for remotely identifying electronically coded articles (e.g., tags, badges and the like). Each of these patents is herein incorporated by reference. The interrogation and identification (I/I) system is comprised of an interrogator/reader (I/R) unit (also referred to as simply an interrogator) and a plurality of badges. The interrogator sends a microwave signal to the badges within a defined area near the interrogator, i.e., the interrogation area. Circuitry within each of the badges processes the interrogation signal and, in response to the interrogation signal, the badges transmit a signal back to the interrogator. From the responsive signal, the interrogator identifies each of the badges by analyzing certain modulation encoded onto the return signal.
More specifically, each of the badges contains a plurality of ID registers (e.g., an A-register, a B-register, and so on) that store unique identification values, i.e., although a particular value in a particular register is not unique, the values in a plurality of registers taken together uniquely identify the badge. The interrogator causes each badge to retrieve the identification values and send the values to the interrogator. To accomplish badge identification, the system performs a "two pass" process. During the first pass, the system generates an interrogation beam to activate the badges within the interrogation area. The system repeatedly sends an interrogation signal that causes the badges to transmit values from their ID registers. This pass causes all the values from each register to be sent, i.e., request the data in all the A-registers of all the badges within the interrogation area, then request data from all the B-registers, then all the C-registers, and so on. The identification values are stored in a computer coupled to the interrogator. The computer then categorizes the values into groups defined by the specific register within the badge from which the value was retrieved, i.e., each returned value is stored in an array that correlates the various values with the various registers. During a "second pass", the categorized groups are sorted by sending particular coding combination to the badges where the coding combination is derived from an analysis of the categorized values. The specific coding combinations uniquely identify the badge that responds to the second interrogation signal.
To accumulate the data from the ID registers, the present system repeatedly polls the badges that are within in the interrogation area to retrieve the register data one register at a time, i.e., all the A-registers are polled, then all the B-registers, and so on. This one-value at a time process is relatively slow.
Therefore, there is a need in the art for a system and method for rapidly identifying a plurality of electronically coded badges.